Adeno-associated virus (AAV) is a small defective DNA virus which requires adenovirus (Ad) as a helper for productive infection. The genome is a linear single strand (MW 1.4 x 10 to the 6th power) which contains a single structural gene. We intend to study the molecular biology of AAV at several levels: 1) Completely determine the sequence of the AAV genome. 2) Map the 3' termini of the AAV RNAs. 3) Determine from overall knowledge of DNA and RNA sequences possible AAV proteins. 4) Clone and sequence the joints formed between AAV and cellular DNAs in latent infection. 5) Look for a specific enzymatic activity which cleaves the hairpin intermediate in AAV DNA replication.